Granular dishwashing detergent compositions and their components, e.g. builders, alkaline salts, sodium silicate, low-foaming surfactant, chlorine bleach, etc., are well known in the art. A number of processes have been described for the continuous production of such dishwashing detergent compositions.
Generally, mechanical mixing processes are less desirable because they result in segregation of ingredients in the package due to differences in the particle size, shape, and density of the detergent ingredients. It has been found that detergent compositions manufactured via a mechanical mixing process exhibit wide variation of detergent ingredients delivered by the composition to the dishwashing solution during actual use. For example, Rapisarda et al U.S. Pat. No. 4,379,069, describes a mechanical mixing process whereby a silicate free alkaline blend of detergent ingredients is prepared followed by mixing of solid alkali metal silicate.
On the other hand, detergent compositions made using agglomeration processes deliver more uniform levels of detergent ingredients during actual use due to the uniform distribution of the detergent ingredients among the individual detergent granules in the composition. See, for example, Porasik U.S. Pat. No. 4,427,417, issued Jan. 24, 1984.
Agglomeration processes for making granular dishwashing detergent compositions described in the prior art generally employ alkali metal silicates as the primary liquid binder. These silicates, as aqueous solutions, provide adhesion properties required in agglomeration processes for the detergent ingredients to form the detergent granules. Unfortunately, compositions manufactured using silicate as the liquid binder sometimes exhibit a high level of insoluble residue due to polymerization of the silicate during drying of wet agglomerates and storage of the detergent composition.
It has now been found that a significant improvement in solubility can be achieved by using a liquid binder other than alkali metal silicate solution, such as an aqueous solution of a water-soluble polymer like sodium polyacrylate. During drying of the wet agglomerates, the water-soluble polymer does not form insolubles like alkali metal silicates do. Further, granules agglomerated with a water-soluble polymer such as polyacrylate will not develop insolubles during storage like base granules agglomerated with the silicate. The alkali metal silicate can be post-added as a dry solid to the agglomerated base product.
It is an object of this invention to use an agglomeration process to produce high bulk density agglomerated dishwashing products containing admixed silicate with significantly improved solubility over agglomerated products made using silicate as the liquid binder.
It is another object of this invention to utilize a liquid binder other than silicate, such as an aqueous solution of a water-soluble polymer like sodium polyacrylate to agglomerate detergent ingredients into granular particles with uniform composition.
Other objects and advantages will be apparent from the following description and examples.